1. Field
The embodiment of the present invention relates to a memory system.
2. Description of the Related Art
As memory systems capable of storing mass data for use, variable resistance memories including cell arrays easily formable in three dimensions, such as a ReRAM (Resistance RAM) and an ion memory, have received attention.
In these memory systems, as one of methods for raising the density of information storage, there is a method of fine pattering a cell array. The use of this method, however, requires higher technologies and causes a problem about cost rises. Another method includes multi-valuing a cell. This method is an effective method because it causes almost no cost rise. In the case of this method, however, physical quantity levels of a cell become unstable. Therefore, unprecedented different ideas are required for writing data to a cell, storing data by a cell and reading data from a cell.